PhysX Force Region Component

You can use the PhysX Force Region component to specify a region that applies physical force to entities. For each physics simulation frame, the component applies force to entities that are in the region’s bounds. You can use this component to simulate effects such as simulating gravity, slowing down, or deflecting an entity to another direction.

To create a force region, you must do the following:

• Enable the PhysX gem for your game project
• Add a PhysX Primitive Collider component to the same entity
• For the PhysX Primitive Collider component, you must select the Trigger property for the force region to work

The PhysX Primitive Collider component’s shape, size, and orientation represent the region that applies force to incoming entities.

Note:

A PhysX Mesh Collider component can also be used, which requires a PxMesh asset. But if the collider inside the asset isn’t a convex mesh (for example, it’s a triangle mesh), the collider won’t work as a trigger for collisions.

Topics

• PhysX Force Region Component Properties
  • Force Types
    • Linear Damping
    • Local Space
    • Point
    • Simple Drag
    • Spline Follow
    • World Space
• Creating a Force Region

PhysX Force Region Component Properties

Force Types

You can add multiple force types to the component. When an entity enters the force region, the entity moves according to the net value of the forces that you specify.

Contents

• PhysX Force Region Component Properties
  • Force Types
    • Linear Damping
    • Local Space
    • Point
    • Simple Drag
    • Spline Follow
    • World Space
• Creating a Force Region

Linear Damping

Applies a force in the opposite direction to an entity’s velocity. For example, you can create a force that simulates a swamp or mud.

Local Space

Applies a force in local space, relative to the force region’s orientation. For example, you can create a force that simulates a hair dryer or a vacuum cleaner.

Point

Applies a force relative to the center of force region. The magnitude determines if the force is inward or outward. For example, you can create a force that simulates an explosion or a black hole.

Simple Drag

Applies a force that simulates air resistance. Simple Drag always applies force in the opposite direction of colliding entities. Larger and faster entities experience more drag. Entities are approximated as spheres.

Spline Follow

Applies a force to make entities follow a spline. The force uses a proportional-derivative (PD) controller that simulates a spring moving along a spline. For example, you can create a force that simulates a water slide.

Note:

For the force region entity, if you change the Scale property of the Transform component, the scaling must be uniform so that the x, y, and z scale values match. If scaling isn’t uniform, the spline doesn’t correctly reflect the path of the force. The end of the spline must be outside the force region so that entities can exit after following the spline.

World Space

Applies a force in world space. World space force doesn’t take into account an entity’s orientation. For example, you can create a force that simulates gravity.

Note:

You can define the direction for world space so that it always applies force in the direction that you want, regardless of the colliding entity.

Note:

When you select a force type, remember the following:

For Simple Drag, you can’t define the direction of force. Simple Drag always works in the opposite direction of the entity’s movement. In contrast, you can define a direction of force using World Space, which always acts in the direction that you specify, regardless of the direction of the moving entity.

To determine how much force to apply, Linear Damping takes into account the colliding entity’s velocity and mass but not its shape. In contrast, Simple Drag takes into account the colliding entity’s velocity, cross-section area, and the Region Density of the force region.

Creating a Force Region

You can create a force region so that force applies to another entity that enters the region.

To create a PhysX Force Region component

1. In O3DE Editor, create an entity.

2. Enter a name for the entity, such as ForceRegion.

3. In the Entity Inspector, choose Add Component and select a PhysX Force Region component.

4. In the PhysX Force Region component, choose Add Required Component and select the PhysX Primitive Collider component.

5. In the PhysX Primitive Collider component, choose Add Required Component and select the PhysX Static Rigid Body component.

6. For the PhysX Primitive Collider component, do the following.

   1. Select the Trigger property.

   2. For Shape, select a shape such as Box.

7. For the PhysX Force Region component, do the following.

   1. Select the Visible and Debug Forces properties.

   2. For Forces, click the + icon and for Force Type, select a force such as Local Space.

   3. For Magnitude, enter a value such as 20.

      Blue arrows appear on the entity that indicate the direction of the force.

      

8. To collide an entity with the force region, create a dynamic entity named Sphere and attach the PhysX Primitive Collider and PhysX Dynamic Rigid Body components. These components enable the entity to interact with other PhysX entities.

9. (Optional) Add a Mesh component and, for Mesh asset, select a mesh asset, such as a _sphere_1x1.fbx.

10. Select and drag the Sphere entity so that it’s above the force region.

    

11. After you create your dynamic entity, press Ctrl+G to enter gameplay mode. Example

    The sphere falls and collides with the force region. The force region applies force and pushes the sphere in the opposite direction.

    

12. To leave gameplay mode, press Esc.

Note:

To display PhysX debug visualizations, see Debugging PhysX. For more information about using PhysX components, see Simulating physics behavior with the PhysX system.